[encoding] revisions to WKT encode

[ear7h]

This would close #81, refer to that issue for more context.

• exposed various encoder options
  • Precision for strconv.FormatFloat
  • Fmt for strconv.FormatFloat, this wasn't talked about but I think it's be helpful
  • Strict see next bullet
• empy points never printed by decoder
  • new strict decoding for stricter error checking
• moved some utility funcitons out of wkt into cmp
• imporoved performance and stability of encoder in removing whitespace
  • I noticed this while running benchmarks on the decoder because it is called by init to decode a tile

There isn't much of a performance difference, most of the cpu time is spent in encodeFloat so slight logic changes don't mean much.

todo: add tests to the cmp functions

[coveralls]

Pull Request Test Coverage Report for Build 384

• 283 of 396 (71.46%) changed or added relevant lines in 4 files are covered.
• 24 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.2%) to 60.004%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
encoding/wkt/wkt.go	0	1	0.0%
cmp/empty.go	80	102	78.43%
encoding/wkt/wkt_decode.go	34	63	53.97%
encoding/wkt/wkt_encode.go	169	230	73.48%
<!--	Total:	283	396	71.46%	-->

Files with Coverage Reduction	New Missed Lines	%
planar/triangulate/constraineddelaunay/triangulator.go	3	58.52%
encoding/wkt/wkt_encode.go	10	65.9%
encoding/wkt/wkt.go	11	23.08%
<!--	Total:	24		-->

Totals
Change from base Build 377:	-0.2%
Covered Lines:	30696
Relevant Lines:	51157

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💛 - Coveralls